The present invention relates to a gas turbine engine, and more particularly to a compact electric starter motor therefor.
Current starting systems for marine and industrial gas turbine engines includes pneumatic and hydraulic start systems. While these systems are effective there may be certain limitations and drawbacks to each. Some of these limitations include: high failure rates; usage of high pressure fluids; lack of accurate speed and torque control during starting, restarting and motoring cycles; and a relatively large overall system space requirements.
Electrical starter systems offers several advantages over pneumatic or hydraulic start systems including: lower overall system volume and cost; higher reliability; improved speed/torque control for starting, re-engagement, and motoring; improved self test and health monitoring; and elimination of potentially hazardous fluids. However, conventional electrical start systems that generate sufficient power to rotate the gas turbine system are relatively large and cumbersome.
A conventional electrical starter includes a central rotor shaft surrounded by a stationary winding (stator). The rotor is supported at each end by bearings mounted outside the axial envelope of the stator. When this arrangement is combined with a separate clutch, the length of the combined shaft, clutch and motor assembly exceeds the axial length available adjacent an industrial gas turbine engine gearbox.
Accordingly, it is desirable to provide a relatively compact electrical starter system that will reasonably fit and operate on the accessory gearbox of a gas turbine engine.